Thread take-up mechanisms for sewing machines



THREAD TAKE-UP MECHANISMS FOR SEWING MACHINES Filed May 14. 1959 Sept. 10, 1963 R. E- JOHNSON 4 Sheets-Sheet 1 I INVENTOR. |*-2 Ralph E. Johnson WITNESS WMW F ig.i Z 3 Z+TORNEY Sept. 10, 1963 R. E. JOHNSON 3,103,191

THREAD TAKE-UP MECHANISMS FOR SEWING MACHINES Filed May 14. 1959 4 Sheets-Sheet 2 INVENTOR. Ralph E. Johnson WITNESS Fi 2 BY ATTORNEY P 1963 R. E. JOHNSON 3,103,191

THREAD TAKE-UP MECHANISMS FOR SEWING MACHINES Filed May 14, 1959 v 4 Sheets-Sheet 5 THREAD CURVES NEEDLE BAR CRANK ANGLE 0 B0TT0M DEAD CENTER INVENTOR.

Ralph E. Johnson WITNESS Sept. 10, 1963 R. E. JOHNSON 3,103,191

THREAD TAKEUP MECHANISMS FOR SEWING MACHINES Filed May 14, 1959 4 Sheets-Sheet 4 INVENTOR. Ralph E. Johnson WITNESS BY ATTORNEY United States Patent Ralph E. Johnson, Mountainside, N..l'., assignor to The Singer Company, a corporation of New Jersey Filed May 14, 1959, Ser. No. 813,107 3 Claims. (Cl. 112-241) This invention relates to thread controlling mechanisms for sewing machines.

Although this invention will be described hereinbelow and illustrated in the accompanying drawings as applied to the needle thread take-up for a lock stitch sewing machine, it will be understood that this invention has advantageous application also to the control of chain stitch sewing threads or to any thread which is concatenated into a machine-produced stitched seam.

It is possible to analyze any given set of stitch forming instrumentalities and to derive the thread requirements during each increment of a cycle of operation so as to formulate a theoretical thread curve indicating the minimum amounts of thread required by the stitch forming instmmentalities. It is also possible to plot and to compare with the theoretical thread curve, .a curve showing the actual amounts of thread which a take-up mechanism does pay out or draw in at any point during a stitch forming cycle. It is a primary object of this invention to provide a thread take-up mechanism with which it is possible to approximate closely any desired actual thread curve with great accuracy throughout all parts of the stitch forming cycle.

In take-up construction and operation, there are many considerations other than the ability to provide the desired thread curve which contribute to the practical success or failure of the device. One such consideration is that of wear or abrasion on the thread by the take-up. Since only a small quantity of thread is used in each stitch as compared with the amount of thread which is drawn in and payed cut during each stitch by the take-up, it is not unusual for an increment of thread to pass back and forth through the take-up dozens of times before it is finally incorporated in the seam.

Since a take-up, if it fails to approximate the theoretical demand curve, must err by providing an excess to avoid certain thread breakage, it follows that an advantage of the take-up of this invention, wherein the theoretical thread curve may be approached with great accuracy, is that the total amount of thread handled during each stitch forming cycle may be materially reduced, thus reducing the number of times that the thread must be drawn back and forth through the take-up and correspondingly reducing the occasion for abrasion.

Furthermore, it is an object of this invention to provide a novel thread take-up mechanism in which only a single thread engaging element such as an eye or a pin contacts the thread. As compared with most rotary takeups in which the thread engages many surfaces and edges, the take-up of the present invention provides only a minute area of surface in contact with the thread, and, consequently, the problems of polishing and maintaininy the thread engaging surfia-ce free of roughness, rust, scratches or contact with abrasives such as dust, lint, etc.

is minimized.

Another consideration in the construction and openation of thread take-ups which influences the practical success or failure thereof is the ease or harshness of the take-up driving mechanism. Thus, in linkage type takeups of the prior art, the take-up motion is vibratory in nature and gives rise to objectionable noise and vibration in the machine operation interfering with smooth operas tion of the machine particularly at the high speeds of Patented Sept. 10, 1963 modern sewing machine operation, and contributing to increased wear in the parts.

It is an object of this invention to provide a take-up mechanism which is actuated in a novel rotary fashion, thus to minimize noise and vibration at even the highest speeds of sewing machine operation.

The present invention comprehends the provision of a single thread-engaging eye or pin on an endless belt which is driven continuously in one direction of rotation in an irregular path as determined by a plurality of idler and driving pulleys.

This take-up thus provides the advantages of vibration- 'free operation of a rotary take-up without the disadvantages of large surface area in contact with the thread. It provides the advantages of close approximation to the theoretical thread curve and the single thread engaging eye or pin of a link take-up without the disadvantage of objectionable vibration, harsh motion and wear experienced therein.

With the above and additional objects and advantages in view as will hereinafter appear, this invention comprises the combinations, devices, and arrangements of parts hereinafter described and illustrated in the accompanying drawings of a preferred embodiment in which:

FIG. 1 represents an end elevational view of a sewing machine having a take-up mechanism of this invention applied thereto,

FIG. 2 is a vertical cross-sectional View taken substantially along line 2--2 of FIG. 1,

FIG. 3 is an enlarged cross-sectional view taken substantially along line 33 of FIG. 1, 7

FIG. 4 is a graph indicating a typical thread demand curve for a lock stitch rotary hook together with a curve illustrating the thread control attained by use of the takeup of this invention in the form illustrated in the drawings, and

FIGS. 5, 6, 7 and 8 represent end elevational views of the sewing machine of FIG. 1 drawn to reduced scale and indicating the position of a needle thread on the take-up at four critical positions of a typical stitch forming cycle, to wit:

FIG. 5 illustrates the stitch setting position,

FIG. 6 illustrates the position at which the work fabric 7 is penetrated by the needle,

FIG. 7 illustrates the position at which the needle thread loop is formed at the needle eye in readiness for seizure by the loop taker, and

FIG. 8 illustrates the position at which the take-up begins to draw the thread up from the loop taker.

Referring to the drawings, FIGS. 1 and 2 illustrate a hollow bracket arm head portion '11 of a sewing machine casing closed by an end cover plate 12. Iournaled in bearings 13 and 14 in the bracket arm is an end-wise reciprocable needle bar '15 carrying a needle :16. The needle bar is reciprocated-by a rotary arm shaft '18 having a counterweight 19 fast thereon and fitted with a crank pin 20 embraced by a needle bar driving link 21 connected to the needle bar by means of a pivot stud 22 clamped on the needle bar.

As illustrated in FIGS. 6, 7 and 8, the needle 16 cooperates in the formation of lock stitches with a loop taker '23 supported beneath the work to be stitched and adapted by mechanism not shown in the drawings to be rotated two revolutions during each needle reciprocation as is conventional in lock stitch sewing machines. The loop taker may be of any known form having a thread carrying bobbin journaled therein, about which bobbin the loop taker carries successive loops of needle thread to produce a seam of interlocked loops of the needle and bobbin threads.

The thread take-up mechanism of the present invention is illustrated in the preferred embodiment of the drawings as used to control the needle thread of a lock stitch sew- 3 ing machine. In the drawings, 30 indicates a polished cylindrical thread engaging pin carried by clips 31-3*1 secured between adjacent transverse teeth 32 of a toothed flexible conveyor or belt 33. The belt is carried on a pair of idler pulleys 34 and 35 which, as illustrated in the drawings, may be of diiierent diameters. Each of the idler pulleys is supported in like manner on the end cover plate 12 by means of a stud 36 having an eccentric extremity 37 extending through an aperture in the end cover plate and with a bearing 38 supporting the idler pulley on the stud. The bearing, which may be a commercial ball bearing, is restrained axially on the stud 36 between a collar 39 abutting the end cover plate and an enlarged head 40 formed on the stud. The idler pulley is constrained axially of the stud 36- on the hearing by means of :a stop ring 41 threaded into the pulley at the opposite side of the bearing from the enlarged head 40 of the stud. The tree extremity of the stud is threaded to accommodate a clamp nut 42 within the hollow bracket arm and the enlarged head of each stud is slotted, as at 43-, to facilitate angular adjustment of the stud to vary the relative arrangement and center-to-center distance between the idler pulleys 34 and 35.

Meshing with the belt teeth along a portion of the belt extending between the idler pulleys is a toothed drive pulley 44 which is accommodated in a circular aperture 45 in the end cover plate 12. The drive pulley is formed with an :arcuate slot 46 and is secured in selected angular position on the free extremity of the needle bar driving crank pin 20 by means of a clamp block 47 secured to the crank pin 20 by means of clamp screws 48 extending through the areuate slot 46.

The number of tooth stations on the drive pulley 44 is preferably made equal to the number of teeth formed on the belt such that in one revolution of the drive pulley the belt traverses one complete turn about the idler pulleys 34 and 35. A gap 49 is formed on the periphery of the drive pulley by the removal of one tooth corresponding to the space occupied on the belt by the clip 31 for the thread engaging pin.

The needle thread is directed from a supply (not shown) through a thread guide 55 on the bracket arm, around a conventional thread tensioning device 56, and over a check spring 57 associated with the thread tensioning device. From the check spring, the needle thread is directed through an elongated wire thread guide 58 secured on the end cover plate '12, over the take-up thread engaging pin 30' and back through the elongated thread guide 58 to a stationary thread guide. 59 on the end cover plate. The thread guides 58 and 59 together provide fixed guides defining a loop of thread to be acted upon by the thread engaging pin 30. From the thread guide 59 the thread is directed through a wire thread guide 60 on the needle bar bearing 14, through the eye of the needle and then to the seam being formed by the machine.

Reference is made to the thread curves illustrated in FIG. 4. Plotted against the needle bar crank angle, the curve labeled Needle and Loop Taker Demand indicates the minimum thread demands of the needle and loop taker over and above that amount of thread which is present at the stitch setting point marked A on the curves for a typical lock stitch sewing machine employing a rotary loop taker of the type illustrated in the drawings. The curve marked tapemp illustrates the amount of thread made available to the needle and loop taker by the take-up of this invention at the various angular positions of the needle bar crank. The vertical distance between the two curves at any crank angle position will indicate the amount of slack thread made available by the take-up at any point in the cycle.

FIGS. to 8 complement the thread curve of FIG. 4, and illustrate the manner in which the take-up serves to control the needle thread at various critical positions during a typical stitch forming cycle.

FIG. 5 illustrates the take-up position when a stitch 4 is being set into the work and corresponds to the point A on the thread curves of FIG. 4.

The point B on the thread curves corresponds to the point at which the needle penetrates the work fabric and the take-up in this position is illustrated in FIG. 6. The thread is payed out of the take-up very gradually between the positions illustrated in FIGS. 5 and 6 to prevent an excess of slack thread which might form a loop at the needle eye, objectionable because of the danger of thread breakage should the needle point enter the loop.

As the thread take-up progresses beyond the position illustrated in FIG. 6, a rapid slackening of the thread occurs to provide for the loop of thread which the needle produces as it descends beneath the work fabrics. As the needle begins to rise, however, and until the loop taker beak seizes the loop from the needle, the rising needle sla-ckens the thread. Immediately preceding the point C in the thread curve, therefore, and as illustrated in FIG. 7, the take up momentarily ceases to pay out thread to prevent an abnormally large amount of slack thread from developing in the system.

The point C on the curves corresponds to seizure of the needle thread loop by the loop taker. The interval from the points C to D :on the thread curve represents the period of rapid expansion of the needle thread loop by the loop taker.

At the point D on the curves which corresponds to the position of parts illustrated in FIG. 8, the loop taker has completely expanded the needle thread loop about the bobbin case containing the bobbin thread means of the conventional lock stitch forming instrumentalities and it remains for the needle thread take-up in the interval from the points D to A on [the curve to draw up the thread into the work.

The position of the parts illustrated in FIGS. 1 and 2 corresponds to the point B on the thread curves, i.e., in that portion of the cycle during which the needle thread is being taken up to set the stitch.

The take-up mechanism of this invention in the form illustrated in the preferred embodiment of the drawings, thus provides ideal control of the needle thread of a lock stitch sewing machine.

One unique and highly advantageous feature of this invention is that the path of motion of practically any portion of the flexible belt or conveyor upon which the thread engaging pin 30 is carried may be modified without affecting the remainder of the path of motion. Thus the seize of the idler pulleys B4 and 35 may be changed, the relative spacing of the idler pulleys may be varied or the spacing of the idlers with respect to the driving pulley may be changed. In terms of the thread curve as illustrated in FIG. 4, this feature of the invention permits any portion of the thread curve to be tailored to suit the needle and loop taker demand at any point in the cycle without disturbing the nature of the thread handling at any other part of the cycle.

The invention is, of course, not limited to the use of two idler pulleys and a single driving pulley. Thus, this invention comprehends the use of a plurality of pulleys, or equivalent means for controlling the path of motion of the belt, disposed to engage either the inside or the outside of the belt. It will be appreciated that by the means herein disclosed, any desired non-circular path may be provided for the thread engaging element of a take-up mechanism which, in conjunction with fixed thread guides, can provide any desired thread control for sewing machine stitch forming instrumentalities.

Having thus described the nature of the invention, what I claim herein is:

1. A thread take-up mechanism for a sewing machine, comprising an endless flexible belt, a plurality of pulleys each engaging the inside of said belt, means supporting said pulleys on spaced parallel axes, to define a noncircular convex path for said belt, at least one pulley engaging the outside of said belt along a portion of said belt extending between two of the pulleys engaging the inside of the belt to define a concave path for said belt, means for driving one of said pulleys, a thread engaging member carried by said belt, and stationary thread guiding means cooperating with said thread engaging member to define a thread loop for engagement with said thread engaging member.

2. A thread take-up mechanism for a sewing machine, comprising an endless flexible belt, a plurality of pulleys of different diameters engaging the inside of said belt, means supporting said pulleys on spaced axes to define a non-circular convex path for said belt, a pulley engaging the outside of said belt, means supporting said last named pulley for engagement with said belt along a portion of said belt extending between two of the pulleys engaging the inside of said belt to define a concave path for said belt, means for driving one of said pulleys, a thread engaging member carried by said belt, and stationary thread guiding means cooperating with said thread engaging member to define a (thread loop for engagement with said thread engaging member.

3. A thread take-up mechanism for a sewing machine,

comprising an endless flexible belt evenly spaced transverse lugs formed on the outside of said belt, a plurality of idler pulleys engaging the inside of said belt, means supporting said idler pulleys on spaced parallel axes, a driving toothed pulley engaging the outside of said belt, said driving belt having teeth of which the number is divisible evenly into the number of transverse belt lugs, means for rotating said driving pulley to impart movement to said flexible endless belt about said idler pulleys, a thread engaging member carried between two adjacent transverse lugs on the belt, said driving pulley having at least one tooth removed corresponding to the space occupied between belt lugs by the thread engaging member, and stationary thread guiding means cooperating with said thread engaging member to define a thread loop for engagement with said thread engaging member.

References Cited in the file of this patent UNITED STATES PATENTS 2,741,133 Barski et a1. Apr. 10, 1956 2,838,946 Kiekhaefer June 17, 1958 2,887,970 Backlin May 26, 1959 

1. A THREAD TAKE-UP MECHANISM FOR A SEWING MACHINE, COMPRISING AN ENDLESS FLEXIBLE BELT, A PLURALITY OF PULLEYS EACH ENGAGING THE INSIDE OF SAID BELT, MEANS SUPPORTING SAID PULLEYS ON SPACED PARALLEL AXES, TO DEFINE A NONCIRCULAR CONVEX PATH FOR SAID BELT, AT LEAST ONE PULLEY ENGAGING THE OUTSIDE OF SAID BELT ALONG A PORTION OF SAID BELT EXTENDING BETWEEN TWO OF THE PULLEYS ENGAGING THE INSIDE OF THE BELT TO DEFINE A CONCAVE PATH FOR SAID BELT, MEANS FOR DRIVING ONE OF SAID PULLEYS, A THREAD ENGAGING MEMBER CARRIED BY SAID BELT, AND STATIONARY THREAD GUIDING MEANS COOPERATING WITH SAID THREAD ENGAGING MEMBER TO DEFINE A THREAD LOOP FOR ENGAGEMENT WITH SAID THREAD ENGAGING MEMBER. 